Process for producing a pharmaceutical solid preparation containing a poorly soluble drug

ABSTRACT

Among the conventional processes for producing solid dispersion, the solid dispersion obtained by a solvent method is excellent in terms of solubility and bioavailability of a poorly soluble drug. However, due to frequent uses of organic solvents in the solvent method, problems have arisen such as organic solvent residue in products, environmental pollution and operational safety as well as corporate problems such as capital investment and the like required to avoid such events. The present invention provides a process for preparing pharmaceutical solid preparations without use of organic solvents frequently used in conventional solvent methods. Specifically, the present invention provides a process for producing a pharmaceutical solid preparation, which is formulated by spraying a solution wherein a poorly soluble drug is dissolved in a plasticizer, and an aqueous solution and/or water dispersion of a water-soluble polymer from nozzle outlets simultaneously and separately in the process for producing the pharmaceutical solid preparation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pharmaceutical solid preparationcontaining a poorly soluble drug for the purpose of improvement ofdissolution and a process for the production thereof, and moreparticularly, to the pharmaceutical solid preparation obtained bydelivering and discharging/spraying an aqueous solution and/or a waterdispersion of a water soluble polymer as well as a plasticizer solutionwherein a poorly soluble drug is dissolved, from nozzle outletssimultaneously and separately, and the process for the productionthereof.

2. Description of the Invention

In light of efficiency and safety, it has been regarded as importantthat significantly high bioavailability is set in the designs forpharmaceutical solid preparations. One of important factors which affectbioavailability of medicines includes solubility of drugs, and numerousstudies have been carried out regarding the relationship of solubilityand digestive tract absorption. In particular, it has been known thatthe dissolution behavior of a poorly soluble drug is a key determinantof its oral bioavailability. Various methods have been studied forformulation techniques of solubility improvement in poorly solubledrugs, and among them, a solid dispersion element method has shownpromise. This method is defined as a method in which a single moleculardrug is dispersed in an inert carrier of a drug in a solid state.Several methods have been proposed for the process of production, andespecially, a solvent method and a mixed pulverization method areincluded as practical methods.

The solvent method is a method for producing a solid dispersion bydissolving a drug and a water-soluble polymer which is a carrier in asolvent such as an organic solvent, and subsequently distilling off thesolvent, or by dissolving the drug in the solvent, dispersing in thecarrier followed by distilling off the solvent. It is believed thatsolubility and bioavailability can be improved because the drug becomesamorphous by dissolving the poorly soluble drug in the solvent and isdispersed in the carrier in such a state.

As specific examples of the solvent method, Japanese Patent Publication(JP-B) Nos. 3-1288/1991 and 3-28404/1991 have reported that the soliddispersion is obtained as follows. Lactose or the like is granulatedwith a water-soluble polymer such as hydroxypropylcellulose to make fineparticles. Nifedipine which is a poorly soluble drug and a polymer basesuch as poly(vinylpyrrolidone), hydroxypropylmethylcellulose andmethylcellulose are dissolved in the organic solvent to form a solution.The solution was sprayed on the fine particles. The sprayed particlesare dried to yield the solid dispersion. Also, in Japanese PatentProvisional Publication (JP-A) No. 281561/2000, the solid dispersion isprepared by dissolving a poorly soluble drug such as cycloheptadines andthe water-soluble polymer such as poly(vinylpyrrolidone),hydroxypropylmethylcellulose and hydroxypropylcellulose in awater/alcohol system, and subsequently spraying on lactose followed bygranulating.

SUMMARY OF THE INVENTION

Among conventional methods for producing solid dispersions, thoseobtained by the solvent method are excellent in terms of solubility andbioavailability of the poorly soluble drug. However, in this solventmethod, because organic solvents such as dichloromethane, acetone andalcohol are frequently used, considerable problems have arisen,including problems of organic solvents residue in products,environmental pollution by organic solvents and safety in operation, andcorporate problems such as capital investment required to avoid suchconcerns.

As a result of an intensive study to solve the above problems, thepresent inventors have found a method for preparing a pharmaceuticalsolid preparation without use of an organic solvent which is frequentlyused in the conventional solvent method. That is, the inventors havefound that a pharmaceutical solid preparation which is excellent indissolution improvement of a drug can be made by being formulated byspraying an aqueous solution and/or water dispersion of a water-solublepolymer as well as a plasticizer solution in which a poorly soluble drugis dissolved from nozzle outlets simultaneously and separately in thepharmaceutical solid preparation. The formulation includes spraygranulation and coating treatment of the preparation. For example,granulated materials or coated particles obtained by granulation orcoating treatment become pharmaceutical solid preparations which areexcellent in dissolution improvement of the drug. According to thepresent invention, the pharmaceutical solid preparation can be preparedwithout use of a conventional organic solvent and by using existingequipment and techniques. Also, it was confirmed that the resultantpharmaceutical solid preparation affords a similar improvement effect ofdissolution as those of the conventional solvent methods.

According to the present invention, a solid solution preparation of apoorly soluble drug can be simply prepared using the existing equipmentand without use of an organic solvent. Also, preparation of the presentinvention has the improved dissolution of a poorly soluble drug comparedto the solid dispersion obtained by the conventional physically mixedmethod, and has solubility equivalent to the solid dispersion obtainedby the conventional solvent method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional drawing of the three fluid nozzle used ina step of fluid bed granulation.

FIG. 2 shows the changes (average values) of dissolution rate ofnifedipine with correlation to time from Examples 1 to 3 and ComparativeExamples 1 and 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The poorly soluble drug used in the present invention is a drug of whichsolubility in water is extremely low and of which absorbability isinferior in normal oral administration, and is referred to, for example,as the drug defined as “nearly insoluble” or “extremely difficult to bedissolved” in Japanese Pharmacopoeia. In Japanese Pharmacopoeia, thesolubility of a drug is defined as the degree of dissolvability within30 minutes when the drug is placed in a solvent and shaken for 30seconds every 5 minutes at 20±5° C. after making powder in the case ofthe drug being solid. “Nearly insoluble” is referred to thecharacteristic where an amount of 10,000 ml or more of the solvent isrequired to dissolve 1 g or 1 ml of the drug. “Extremely difficult to bedissolved” is referred to the characteristic where a solvent amount of1,000 to 10,000 ml is required to dissolve 1 g or 1 ml of the drug.Specifically, for example, such drugs include nifedipine, phenacetin,phenytoin, digitoxin, nilvadipine, diazepam, griseofulvin andchloramphenicol.

Plasticizers used in the present invention include propylene glycol,polyethylene glycol, triethyl citrate, acetyl monoglyceride, glycerine,tributyl citrate, triacetin, diacetin, monoacetin and diethyl phthalate,which may be used alone or in combination of two or more.

These plasticizers are added aiming at improving the plasticity ofpolymer films and added for the purpose of improving the uniformity ofgranulations or coating films. Amounts are not especially limited aslong as it is an additional amount required to achieve the purpose.However, it is desirable that the minimum weight part to significantlydissolve the drug in the plasticizer is added ranging from 1 to 20weight parts, preferably from 7 to 15 weight parts based on one weightparts of the drug used.

The solution in which the drug used in the present invention isdissolved in the plasticizer is preferably the solution in which thedrug and the plasticizer are dissolved at the above weight ratio.However, surfactants, oils, fats or the like can be included for thepurpose of further improving the solubility of the drug.

The water-soluble polymers used in the present invention include, forexample, cellulose derivatives such as methylcellulose,hydroxypropylcellulose, hydroxypropylmethylcellulose,hydroxypropylmethylcellulose phthalate, hydroxypropylmethylcelluloseacetate succinate, ethylcellulose, hydroxyethylcellulose and sodiumcarboxymethylcellulose; poly(vinylpyrrolidone); and poly(vinyl alcohol).Among them, hydroxypropylmethylcellulose acetate succinate,hydroxypropylmethylcellulose phthalate, hydroxypropylmethylcellulose andpoly(vinylpyrrolidone) are polymers effective for dissolution of thedrug. Also, a mixture of these water-soluble polymers can be used asappropriate.

The fineness of these water-soluble polymers is not especially limitedas long as it does not block up a spray gun when used as a dispersion,and the average particle diameter may be 100 μm or less, and preferably50 μm or less.

The aqueous solutions of the water-soluble polymers include the aqueoussolution obtained by dissolving in a weak alkali aqueous solution suchas an ammonia solution. It is desirable that the solution is prepared at5 to 30% by weight. In the dispersion of the water-soluble polymer, saidpolymer can be dispersed in a given amount of water with stirring, andthe concentration is not especially limited but a concentration at 5 to30% by weight may be preferred.

The combination ratio of the poorly soluble drug to the water-solublepolymer in the pharmaceutical solid preparation of the present inventionis appropriately determined depending on the types of the poorly solubledrug and water-soluble polymer. It may be from (1:0.1) to (1:10), andpreferably from (1:0.5) to (1:5) as a weight ratio. When the combinationratio of the water-soluble polymer is lower, recrystallization of thedrug may be precipitated in the pharmaceutical solid preparationresulting in lowering the dissolution. When it is higher, it may not bepreferable because dissolution may not be significantly improved and thepharmaceutical solid preparation may be bulky leading to increaseddosages.

Formulation of the present invention includes coating treatment andspray granulation of the preparation. The types of preparationssubjected to coating are not especially limited, but solid preparationsuch as tablets, granules or capsules may be preferable for performinguniform coating. Those subjected to spray granulation include powderbodies and nuclei of lactose, sucrose, glucose, trehalose, fructose,dextrin, starch, pullulan, carboxymethylcellulose and salts thereof,carboxymethylstarch and salts thereof, cellulose, poly(vinylalcohol) andhemicellulose.

The amount of coating varies depending on the types of solidpreparation. An amount of 3 to 50% by weight as the solid content may bepreferable based on the weight of the solid preparation. In the case ofcoating the solid preparation, coating of the solid preparation may becarried out using another coating agent such ashydroxypropylmethylcellulose prior thereto.

The process for producing the solid dispersion preparation of thepresent invention can advantageously produce the pharmaceutical solidpreparation when, for example, the spray gun shown in FIG. 1 is used.

This has a construction such that the water-soluble polymer dispersionand/or the water-soluble polymer solution and the plasticizer solutionare appropriately selected and inserted via a pump through a liquid Ainlet 1 and a liquid B inlet 2, respectively. The liquid A inlet 1 andliquid B inlet 2 are linked to a nozzle outlet of A nozzle 4 and anozzle outlet of B nozzle 5, respectively, and liquid A and B aredischarged/sprayed. Air from an air inlet 3 is discharged through anozzle outlet of an air nozzle (cap) 6. In FIG. 1, the nozzle outlets ofA nozzle 4, B nozzle 5 and air are in approximately concentric circlesand arranged from the inside to the outside. FIG. 1 also shows an O ring7 and a gasket 8. There may be an embodiment where the water-solublepolymer dispersion and/or water-soluble polymer solution is used asliquid A and the plasticizer solution is used as liquid B. Conversely,there may be also an embodiment in which the plasticizer solution isused as liquid A and the water-soluble polymer dispersion and/orwater-soluble polymer solution is used as liquid B.

The pump to insert the water-soluble polymer dispersion and/orwater-soluble polymer solution and the plasticizer solution is notespecially limited, and a commonly available one is used. It may bepreferable to use a gear pump or a tube pump.

Materials of the spray gun used in the present invention are notespecially limited as long as they are water-proof and are not dissolvedand melted in the plasticizer at a temperature from room temperature toaround 100° C. Heat-resistant materials such as stainless steel, whichresists rust, and silicone may be preferable.

The shape and diameter of the nozzle are not especially limited as longas they are capable of spraying. A diameter for ease in spraying or adistance of 0.1 to 5 mm between the tube walls may be preferred.

The rate of the delivered solution from the spray gun is not especiallylimited, but the rate of a few g/min to some 100 g/min may be preferredas a rough standard to be easily formulated in general. There may be noconcerns even in the case of a construction where air or gas forspraying can be supplied to the nozzle. The supplied amount of air orgas is not especially limited as long as it is in a range capable ofspraying, but the amount of some 10 liters/min to some 100 liters/minmay be preferable. Types of gas other than air are not especiallylimited, but a inert gas such as nitrogen or helium which is lessinteractive with the drug may be preferable.

By using this spray gun, common formulation machines equipped with thesystem to spray/dry the liquid may be used as such.

Fluid bed granulation equipment, pan coating equipment, coatingequipment incorporated with a ventilation dry system, and fluid coatingequipment can be used as equipment for formulation.

In order to further make the prepared solid preparation into tablets,those usually used thereafter in the field of preparations, other thanthe poorly soluble drug and water-soluble polymer, for example, anexcipient such as lactose, corn starch, crystalline cellulose,D-mannitol and erythritol; a disintegrant such as low substitutedhydroxypropyl cellulose, cross carmellose sodium, carmellose calcium andcross povidone; a pigment; perfume; a sweetener; may appropriately beadded to the pharmaceutical solid preparation of the present inventionif necessary.

Examples and Comparative Examples are shown below, and the presentinvention is described in detail, but the invention is not limitedthereto.

EXAMPLE 1

The poorly soluble drug, nifedipine (10 g)(supplied by Daito Co., Ltd.)was dissolved in a mixture solution of the plasticizer, polyethyleneglycol 400 (96 g) and triethyl citrate (4 g) to make Spray A solution.As the water-soluble polymer solution, a dispersion made of 6 g of talc,0.2 g of sodium lauryl sulfate and 107.1 g of purified water for 20 g ofhydroxypropylmethylcellulose acetate succinate (HPMCAS)(AS-MF: suppliedby Shin-Etsu Chemical Co. Ltd.) was prepared to make Spray B solution.Lactose (200 g) (lactose 200M: supplied by DMV Co., Ltd.) was fluidizedin a fluidized-bed granulation machine (equipment name: Multiplex:supplied by Freund Industrial Co., Ltd.: Multiplex MP-01), and bothSpray A and B solutions were sprayed to granulate in a manner of sidespraying using three fluid nozzles (spray gun) shown in FIG. 1. Spray Asolution, Spray B solution and compressed air were supplied to threefluid nozzles by a tube pump from the outside. Solutions A and B andcompressed air were passed through the solution lead-in path A and Bnozzles and the air lead-in path (cap), respectively, and were sprayedas spray solutions which spread over concentric circles.

After granulation, the granules were selected by a 14-mesh sieve toyield preparation containing nifedipine.

The manipulation condition was as follows.

Spray gun: identical to the spray gun shown in FIG. 1. One having aninternal diameter of 2.5 mm as A nozzle and one having an externaldiameter of 2.0 mm and the internal diameter of 1.0 mm as B nozzle wereused.

Temperature of Spray A and B solutions: 27° C.

Dry air temperature: 70 to 80° C.

Rate of supplying air to the spray gun: 2.5 liters/min

Rate of supplying Spray A solution: 5 g/min

Rate of supplying Spray B solution: 4.1 g/min

Manipulation: 40 minutes

Used amount of HPMCAS: 2 fold by weight based on major component(nifedipine)

EXAMPLE 2

Granulation was carried out to obtain the nifedipine containingpreparation in the same manner as that in Example 1, except that theaqueous solution of the water-soluble polymer was made by dissolving 20g of hydroxypropylmethylcellulose (TC-5R: supplied by Shin-Etsu ChemicalCo. Ltd.) in 180 g of purified water to render Spray B solution.

EXAMPLE 3

Granulation was carried out to obtain the nifedipine containingpreparation in the same manner as that in Example 1, except that 200 gof lactose in Example 1 were replaced with the mixed powder of 170 g oflactose and 30 g of Hydrated Silicon-Dioxide (Carplex #80: supplied byShionogi & Co. Ltd.).

COMPARATIVE EXAMPLE 1

10 g of Nifedipine and 20 g of hydroxypropylmethylcellulose acetatesuccinate were dissolved in 300 g of mixed solvents of dichloromethaneand ethanol (weight ratio 1:1) to render a spray solution. Lactose (200g) was fluidized in a fluid bed granulation machine, and the spraysolution was sprayed to granulate in the manner of side sprayingfollowed by being selected by a 14-mesh sieve to yield a preparationcontaining nifedipine.

COMPARATIVE EXAMPLE 2

10 g of Nifedipine, 20 g of hydroxypropylmethylcellulose acetatesuccinate and 200 g of lactose were mixed in a mortar to yield thenifedipine containing preparation physically mixed and powdered.

TEST EXAMPLE

The following test was carried out for the preparations of Examples 1 to3 and Comparative Examples 1 and 2.

(1) Samples: preparations of Examples 1 to 3 and Comparative Examples 1and 2.

(2) Test method: as the test solution, 500 ml of the second solution (pH6.8) described in Japanese Pharmacopoeia was used. Each samplecorresponding to 10 mg of nifedipine was added thereto, and a test wascarried out according to the second method of the dissolution testmethod (paddle method) of Japanese Pharmacopoeia. The rotationalfrequency of the paddle was 100 rpm. For each constant time elapsed (0,10, 20, 40, 80 minutes), 2 ml of solution was collected, to which asecond solution was added up to a total volume of 10 ml to dilute 5times. Subsequently, the dissolution amount of nifedipine was determinedby measuring an absorbance at wavelengths of 325 nm and 500 nm using anautomatic dissolution tester (Shimadzu UV-160: supplied by ShimadzuCorporation).

For an evaluation of dissolution rate improvements, those which provideda supersaturated solubility which exceeds the saturated solubility ofnifedipine (10 mg/ml) and showed an dissolution rate of 75% or more ofthe drug in preparation in the results of the above dissolution testwere considered “good”.

(3) Results of the test: changes of dissolution rate of nifedipine withcorrelation to the time elapsed (mean values of three points) are shownin FIG. 2.

As is obviously shown in FIG. 2, the preparation according to thepresent invention can provide a supersaturated solution which exceedsthe saturated solubility of nifedipine (Comparative Example 2), andmaintain the supersaturated concentration without a decrease withcorrelation to the time elapsed. Also it has been shown that preparationof the present invention has a drug solubility improvement effectcomparative to that of the preparation (Comparative Example 1) by thesolvent method using an organic solvent of which the effect has beenconfirmed.

1-4. (canceled)
 5. A pharmaceutical solid preparation produced byspraying from nozzle outlets simultaneously and separately 1) a solutionof a poorly soluble drug dissolved in a plasticizer, and 2) an aqueoussolution and/or water dispersion of a water-soluble polymer.
 6. Thepharmaceutical solid preparation produced by the process according toclaim 5, wherein said plasticizer is selected from a group consisting ofcitrate esters, glycerine esters, phthalate esters and polyvalentalcohols.
 7. The pharmaceutical solid preparation produced by theprocess according to claim 5, wherein said water-soluble polymer isselected from the group consisting of cellulose derivatives andpoly(vinylpyrrolidone).
 8. The pharmaceutical solid preparation producedby the process according to claim 6, wherein said water-soluble polymeris selected from the group consisting of cellulose derivatives andpoly(vinylpyrrolidone). 9-11. (canceled)